Braking systems are required for towed vehicles such as trailers and the like where the brakes of the towing vehicle are not sufficient to provide adequate braking for the added weight of the towed vehicle.
Surge or inertial braking systems use the force exerted by the towed vehicle on the towing vehicle through the tow hitch apparatus to activate brakes on the towed vehicle. Such surge braking systems are disclosed for example in U.S. Pat. No. 4,889,212 to Temple, U.S. Pat. No. 7,806,240 to Walstrom, et al., and U.S. Pat. No. 8,708,112 to Maisonneuve.
Electronic braking systems for towed vehicles are also known where a variety of sensors determines when braking of the towed vehicle is required, and activates the towed vehicle brakes. Such electronic braking systems are disclosed for example in U.S. Pat. No. 8,267,485 to Barlsen, et al. and U.S. Pat. No. 8,540,323 to Broch, et al.
Large agricultural air seeders typically include a product cart carrying product tanks that, when full of agricultural products, weigh well over twice as much as the tractor towing the air seeder. Larger product carts are sometimes mounted on tracks to reduce soil compaction. The product cart can be towed either behind the furrow opener implement of the air seeder, or between the furrow opener implement and the tractor, such that a train of towed vehicles is formed. In addition to the product cart and furrow opener, it is common to add another tank specifically for carrying fertilizer in its gaseous or liquid form. Braking systems are necessary to control the train, particularly during transport when the equipment is rolling freely behind the tractor on inclined ground surfaces.
A train including a product cart, furrow opener implement, and extra fertilizer tank can outweigh the towing tractor by over 1.5 times when empty and when this heavy train is being towed at high transport speeds, it can cause control issues. Due to the heavy weight of the unloaded train and the high transport speeds that can be achieved, an unloaded implement train can still be hazardous. Because of the heavy weight of the cart and the considerable distance between the tractor as a braking power source and the cart, providing effective braking for air seeders using conventional towed vehicle braking systems is problematic.